Thermal deformation behaviour and physically-based dual-phase constitutive model of Ni/Ni2Al3 laminated composites

To investigate the high-temperature deformation behaviour of Ni/Ni 2 Al 3 laminated composites with greater precision, a series of uniaxial tensile experiments was conducted at 700 °C under various strain rates of 0.001 s -1 , 0.002 s -1 , 0.005 s -1 , and 0.01 s -1 to obtain the evolution of flow stress and fracture elongation. Experimental results indicated that the material exhibited uniform deformation and superplastic deformation behaviour under high-temperature loading conditions. With an increase of strain rate from 0.001 s -1 to 0.01 s -1 , the elongation of fractures exhibited a gradual tendency of decreasing from a peak of 249.5%, with an increasing tendency of the highest flow stress from 85.4MPa to 147.3MPa. To elucidate the microstructural evolution during deformation, scanning electron microscopy and electron backscatter diffraction were conducted on specimens to examine the microstructural evolution before and after deformation. These characterisations demonstrated that dynamic recrystallisation and dislocation pile-up occurred concurrently in both Ni and Ni 2 Al 3 phases during the high-temperature deformation process. A dual-phase viscoplastic constitutive model was developed based on macroscopic and microscopic experimental data, incorporating the evolution of physically-based internal state variables. The model successfully predicted the high-temperature stress-strain behaviour of the Ni/Ni 2 Al 3 laminated composites, achieving a prediction accuracy of 98.79%. Moreover, the model accurately predicted the grain size evolution within individual phases, offering a mechanistic insight into the deformation response of each constituent phase. The proposed modelling framework provides a robust theoretical basis for optimising thermal-mechanical processing and the numerical simulation of Ni-Al intermetallic composites. Beyond the present analysis, the methodology can be adapted to construct predictive models of Ni–Al intermetallic composites tested at 700 °C with different strain rates, providing the quantitative evaluation of mechanical performance and dual-phase microstructural evolution during the high-temperature manufacturing process.